54 A PAPER ON EGGS, 



elegant blue that distingiiislies the eggs of the Fire-tail {St/Ina 

 Phoenicurus, Latham), and of the Hedge SpaiTOW, though cor- 

 roded away, is not destroyed, with mimatic acid. 



" The blue calcareous coating of the Thrush's egg is consumed, 

 but the dark spots, like the markings on the eggs of the Yellow 

 Hammer, House Sparrow, Magpie, etc., stil] preserre their sta- 

 tions on the film, though loosened and rendered mucilaginous by 

 this rough process." 



Mr. "W. C. Hewitson* says, '' That the colouring of bird's eggs 

 is an animal matter, and dependent on the health of the bird, 

 there can be little doubt. The day previous to theii- being pro- 

 duced and after the shell has become hard, they are, in those 

 bii'ds that I have examined, pure white ; a large proportion of 

 the colour also is easily rubbed off, for some time after they have 

 been laid. Thus we find in their eggs the same want of colour, 

 which is also occasionally observable in the feathers of white va- 

 rieties of birds. Fear, or anything that might affect the animal 

 functions, exerts its influence upon the colour also. The eggs 

 of birds I have captured on their nests, during the time they 

 were laying, and kept in close confinement, have thus been de- 

 pnved of much of their colour." 



Professor Floui'ens,f in his Lectures, has the following passage, 

 which I met with December 7, 1870, "La coloration bizaiTe, 

 variee a Tinfini des coques des o\'ipares, parait tenir ou a des 

 echappees sanguines hors des vaisseaux de I'oWducte, et u la 

 oorabinaison de sels metalliques, on ]dut6t etre le resultat d'une 

 secretion particuli«'Te." 



Professor Owen J tells us that "The colour of tlie o^^ shell 

 depends on pigmental matter secreted by particular follicles of 

 tlie villous membrane of the ' uterus ;' and either incorporated 

 uniformly with the outermost layer of the shell, as in the Thrush, 

 or deposited in cells more or less dispersed or aggregated in 

 patches." 



• Coloured Illiititrallons of the EjfS* of Brit. Hlnlii. Hi-.l Edit., Lond., 184fi, Vol. I., 

 Introd., |>. Vlf. 



t Conr» sur In n(5ndration l"0%-ylo}.'lo, etc.. pulil. pnr Dc5champ< I'jirli, 183<>. 



Anntomy of VortrJ»rato«, Vol. II.. p. •j'»4. 



